PURPOSE: To prevent cracking in the root part of a vane surface by forming an impeller to a formable shape by pressure casting, providing the 1st recess and the 2nd recess on both sides in the root part of the vane shape thereof, and raising said parts.

CONSTITUTION: An impeller 1 is formed to a formable shape by pressure casting, and a vane shape 2' is raised to form a completed vane 2. The 1st recessed surface 10 which is depressed so as to be continuous to the radial position shown by a line (b) with the approximate arc line from the vane surface 2A is formed in the root part on the vane surface 2'A side in the end part on an inducer side. The 2nd recessed surface 20 is formed so as to be continuous to the vane surface 2B after the raising like in the radial position shown by the line (b) in the root part on the vane surface 2'B side which is a front surface when viewed in the raising direction. The surfaces 10, 20 are made continuous smoothly to an arc shape along the line (b). The stress to be generated in the raising is thus reduced and the generation of cracking is prevented.